Limit stop for shiftable platens



April 1927' o. A. HOKANSON LIMIT STOP FOR SHIFTABLE PLATENS Filed April 28. 1923 Patented Apr. 19, 1927.

8 UNITED STATES tense? PATENT OFFICE.

I OTTO A. HOKANSON, 0F WOODSTOCK, ILLINOIS, TO WOODSTOCK TYPEWRITER COMPANY, OF WOODSTOCK, ILLINOIS, A CORPORATION OF ILLINOIS.

LIMIT STOP FOB SHIFTABLE PLATENS.

Application filed April 28, 1923. Serial No. 635,273.

This invention relates to stop mechanism for limiting the movement of a typewriter platen by which the platen is shifted for upper and lower case writing.

The invention has for its object the provision of a stop by which the jar and noise incident to case shifting is reduced to a minimum and which shall be of improved construction and operation.

The invention is exemplified in the combination and arrangement of parts shown in the accompanying drawing and described in the following specification, and it is more particularly pointed out in the appended claims.

In the drawing Fig. 1 is a fragmentary end view of a portion of a typewriter carriage showing the stop mechanism of the present invention in elevation; and

Fig. 2 is a front elevation, with parts broken away, showing the mechanism illustrated in Fig. 1.

The drawing illustrates the invention as applied to the present form of Woodstock typewriter now on the market, but it Will be understood that the invention is not confined to any particular make of typewriter, but is applicable to various makes.

In the drawing, the numeral designates the guide rails upon which the platen carriage 11 is mounted for lateral movement. A pair of arms 12 and 13 are pivoted at 14 and 15, respectively, on the platen carriage 11 andhave pivotal connection at 16 and 17 with the shift frame 18 which carries the platen 19 journaled at 20 there in. It will be seen that the arms12 and 13 provide a parallel link movement for guiding the shift frame 18 when it is moved vertically for case shift.

A bracket 21 extends the shift frame 18 and carries a roller which rests upon a shift bar 23 and travels with the carriage. Suitable mechanism 24 of well-known construction is operated by the shift key for raising the bar 23 to shift for upper case letters.

A stop arm 25 is pivoted on a stud 26 secured to the end member of the platen carriage 11. The arm 25 is bifurcated at its forward end to receive a stud 27 carried by the shift frame 18. It will be understood that a stop'bar is provided at each end of the platen carriage. The bar 25 downwardly from carries a laterally bent lug or stop 28 interposed between adjustable limit screws 29 and 30. These screws are threaded in spaced portions of the frame 11 and are provided with lock nuts 31 and 32 for lockmg the screws in adjusted positions.

The bar 25 constitutes a lever of the third class for supporting the platen, and the stops 28 with their co-operating parts, operate without assistance from any other stops for arresting the case shift movement of the platen.-

It will be seen that the arm 25 operates to reduce the movement imparted to the stop 28 to an amount much less than the total movement of the shift frame. The amplitude of movement of stop 28 as compared to that of the shift frame will have the ratio of the distances of the stop 28 and pivot 27, respectively, from the pivotal mounting 26. In the drawing, the proportions illustrated will produce a movement of the stop 28 approximately equal to onethird of the amplitude of the shift frame movement, but these proportions may, of course, be varied to suit different conditions. This reduction in amplitude of movement of the stop member has been found in practice to reduce the noise and jar incident to case shift to such a degree that it is practically negligible.

I claim 1. A typewriter having a member mounted thereon for case shift movement, a stop for limiting the movement of said member, lever mechanism for connecting said stop with said member and arranged to impart a reduced movement to said stop, and spaced abutment members for limiting the movement of said stop.

2. A typewriter comprising a platen carriage, a case shift frame mountedon said carriage, an arm having spaced pivotal connection with said' case shift frame and platen carriage respectively, a stop on said arm, and abutment members for engaging said stop to limit the movement of said arm and case shift frame.

3. In combination, a typewriter, a platen support mounted on said typewriter and movable relative thereto for effecting case shift, a lever pivotally mounted on said typewriter and engaging said platen support at a point spaced from its pivotal connection with said typewriter, and a limit stop carried by said lever and spaced from said pivotal connection an amount less than the distance between said pivotal connection and the connection between said lever and said movable platen support.

-1l. The combination with a platen carriage, of a shift flame movably mounted on said nrriage, a platen jonrnaled in said shift frame, an arm pivotally mounted on said platen carriage, means for connecting said arm with said shift frame at a point spaced from the pivotal connection with said platen carriz'tge, a stop n'iounted on said arm between its; point of connection with said shift frame and its pivotal connection with said platen carriage, and ad justable almtment members for limitingthe movement of said stop when said shift frame is moved for ase shift.

in a tvpewriter, a platen carriage, a shift frame having a platen mounted thereon, parallel link mechanism for connecting said carriage and frame, an arm pivotally mounted on said calriage adjacent one end thereof and having bifurcations for engaging a pivot: stud on said shift frame, a stop lug carried by said arm at a point intermediate the PlVO E/t l connections thereof With said platen carriage and shift frame, limit screws threaded in said platen carriage and :l'orming opposed abutn'ients for engaging said stop, and means for locking said limit screwsiin adjusted positions.

(3. In combination, a typewriter frame having a'platen carriage mounted to travel thereon, a platen supporting frame, means "for connecting said frame with said carriage for vertical movement relative thereto, case shift. mechanism for moving said frame, an arm having horizontally spaced pivotal connections with said platen carriage and flame, the pivotal coimection with one of said members being arranged to permit slie'htlateral movement, a stop on said arm spaced nearer the pivotal connection with said carriage than it is to the pivotal connection with said frame, and adjustable abutment members for limiting the move ment of said stop.

In testimony whereof I have signed my name to this specification on this 26th day of April, A. D. 1923.

OTTO A. HOKANSON. 

